In response to user requests, I just released Moray, a script which uses CaRP and Grouper to filter and aggregate RSS feeds, and republish them in RSS 2.0 format. It's a free download, and can be used with the free version of CaRP, but requires the commercial version of Grouper ($17.97 for a single user). It works better if you have one of the commercial versions of CaRP, since without them, the resulting feed won't contain date or author elements.

Why "Moray"? Because moray eels eat young grouper, and Moray eats RSS feeds, which is what Grouper outputs. Moray eels also eat other moray eels...